1. Field of Invention
The present invention relates generally to fuel charging systems for an internal combustion engine, and more particularly to fuel charging systems with reduced pulsation magnitudes at resonant modes of the fuel charging system.
2. Description of the Known Technology
Conventional methods of damping pressure pulsations in a fuel system rely solely on inclusion of a member that introduces more compliance, thereby reducing the bulk modulus of the system. This is often accomplished through the use of a flexible wall or walls in a member that is in liquid communication with the pulsating fuel to absorb the pressure fluctuations within the system.
However, a problem arises when the injector frequency excites one of the various resonant modes of the fuel system. At these frequencies, the maximum pressure pulsation magnitude can increase to several times normal operating levels. Attempting to resolve these resonant frequency issues simply by adding more compliance can result in other unwanted effects. Adding more compliance may allow more pulsations to be absorbed, but it will also result in a shift in resonant frequency. As compliance is increased, the resonant frequency modes shift to lower frequencies. When the modes shift lower, higher modes that were previously above the operating frequency range of the fuel system may shift into the operating frequency of the fuel system. Therefore, adding more compliance can sometimes result in more objectionable resonant frequency than before.
The solution to this problem, as shown in U.S. Pat. No. 6,848,477 to Treusch et al., includes one or more restrictors that work in conjunction with the system compliance dampers or inherent compliance to achieve the desired damping of pressure fluctuations. However, for fuel charging systems with dual-bank rail configurations, it may be found that when the engine is operating under heavy loads, an undesirable pressure difference between the two rails of a dual bank rail configuration may result. This pressure differential between the fuel rails causes different amounts of fuel to be injected into the two engine banks, altering the air/fuel ratio resulting in reduced fuel economy and emissions concerns.
Therefore, there is a need for a solution that introduces the desired damping of pressure fluctuations while minimizing the pressure differential between the fuel rails of a dual-bank rail configuration.